The invention is based on a pneumatic diaphragm control element for a fuel injection apparatus in internal combustion engines, in particular supercharged Diesel engines.
In so-called supercharged engines, a pneumatic diaphragm control element of this kind acts as a charge-pressure-dependent full-load stop (CPS), which serves to reduce the quantity of fuel pumped at full load beyond a predetermined charge pressure, in the lower rpm range. The diaphragm control element may be mounted on the fuel injection pum of the fuel injection device and act via a control member on a supply quantity adjusting member, or it may be flanged to a centrifugal governor of the fuel injection apparatus and act via a control member on a governor lever, which in turn controls the supply quantity adjusting member.
In a known diaphragm control element of the above type (German Offenlegungsschrift No. 28 37 964), the counterpart stop is embodied as an adjusting nut that can be screwed onto an externally threaded portion of the thrust rod, and the adjusting nut is fixed on the thrust rod with a check nut after the maximum displacement travel of the thrust rod has been set. With the construction of the known diaphragm control element, it is possible to separately set the full-load quantity without charge pressure (the so-called intake quantity), the full-load quantity at full charge pressure (the so-called charger quantity), and the effective pressure range. The intake quantity is defined by means of the length of the stop screw that protrudes into the pressure chamber; the charger quantity is defined by the relative position of the adjusting nut on the thrust rod; and the pressure range is defined by the initial stress of the restoring spring, which can be adjusted by means of abutments.
However the known diaphragm element has only a linear adjusting characteristic within the effective pressure range; that is, the adjusting travel of the thrust rod is linearly dependent on the charge pressure prevailing in the pressure chamber, which is frequently inadequate in terms of the need to influence or control the fuel supply quantity.